Highly stretchable, self-healing and conductive silk fibroin-based double network gels via a sonication-induced and self-emulsifying green procedure

Regenerated silk fibroin (RSF)-based hydrogels are promising biomedical materials due to their biocompatibility and biodegradability. However, the weak mechanical properties and lack of functionality limit their practical applications. Here, we developed a tough and conductive RSF-based double network (DN) gel, consisting of a sonication-induced β-sheet physically crosslinked RSF/S gel as the first network and a hydrophobically associated polyacrylamide/stearyl methacrylate (PAAm/C18) gel as the second network. In particular, the cross-linking points of the second network were micelles formed by emulsifying the hydrophobic monomer (C18M) with a natural SF- capryl glucoside co-surfactant. The reversible dynamic bonds in the DN provided good self-healing ability and an effective dissipative energy mechanism for the DN hydrogel, while the addition of calcium ions improved the self-healing ability and electrical conductivity of the hydrogel. Under optimal conditions, the RSF/S-PAAm/C18 DN gels exhibited large extensibility (1400%), high tensile strength (0.3 MPa), satisfactory self-healing capability (90%) and electrical conductivity (0.12 S·m(−1)). The full physically interacted DN hydrogels are expected to be applied in various fields such as tissue engineering, biosensors and artificial electronic skin.